Research Of Downhole Video Logging Instrument

Downhole video is a kind of logging instrument that taking images under the shaft. By the processing of electronic circuit, these images will reach the ground. This article is focused on the present video imaging logging system based on common logging cable is not a real-time transmission instrument. To solve this problem, this paper has designed a kind of logging instrument that based on the of optical fiber communication. It has solved some problems, such as:Discrete, reduction of video signal, the digital optical fiber transmission, lighting, the lens separated oil. The main research contents of this paper are as follows:1. The digital coding technology and optical fiber transmission technology is applied to the downhole video. This downhole video transmit4digital signals in a single fiber, by using AD9280high-speed A/D chip to discrete analog video signal and time division multiplex technology. To the ground, the device receives these digital signals and transform them to the analog video signals.2. In optical fiber communication, bipolar code is suitable for cable transmission.But unbipolar code is suitable for optical fiber transmission.To solve this problem, this paper introduces8B10B coding technology for digital signal type transformation, improve the level of jump density, meet the requirements of the optical fiber transmission of type.3. Using FPGA+ASIC chips to design this device. These methods are applied to the device, video filter, separation, D/A, A/D, Serial/Paraller, Paraller/Serial conversion. PCB with four layer board plate structure and high speed serial data interface using PECL difference exchange coupling connection mode. The system has the characteristics of integration, high reliability. 4. According the oil well diameter is small so testing instrument cannot be designing too large. This paper designs the instrument shell under the SolidWorks software.5. On the experimental platform, under the instrument pressure on cylinder and constant temperature box, I have did the heat resistance,compression tests on the optical fiber, circuit, glass lens. The system has stable performance, under the136℃,25Mpa pressure environment and it reaches the design requirements. Comparing several lens glass anti-fouling processing measures, knows lens painted with oil paint is resistant to water and soil.